The present invention relates to a high-quality titanium target for sputtering capable of significantly reducing the impurity concentration of gas components such as oxygen, nitrogen and hydrogen contained in the titanium target for sputtering, and effectively suppressing the formation of particles upon deposition.
The impurity concentration of gas components such as oxygen, nitrogen and hydrogen described in the present specification will be displayed in mass% in all cases.
In recent years, various electronic devices have been devised beginning with the exponential advancement of semiconductors, and the improvement of such functions as well as the development of new devices are being sought on a daily basis.
Under these circumstances, there is an inclination toward the miniaturization of electronic devices and equipment and increase in the degree of integration thereof. Numerous thin films are formed during the manufacturing process of many of such devices and equipment, and titanium, from its unique metallic property, is used in the formation of thin films of various electronic devices as titanium and its alloy film, titanium silicide film, or titanium nitride film.
Upon forming such titanium (including metal alloys and compounds) films, attention must be given to the fact that the titanium film itself requires a high degree of purity.
The thin films used in semiconductors and the like are made even thinner, shorter and smaller, and, since the mutual distance thereof is extremely small and the integration density is being improved, there is a problem in that the substance forming the thin film or the impurities contained in such thin film will diffuse to the adjacent thin films. This will result in the off-balance of the constituents of the original film and the adjacent films, and there is a significant problem in that the primary function of the film will deteriorate.
In the manufacturing process of this type of thin film, there are cases where the application of heat reaches several hundred degrees, and the temperature also rises during the use of electronic devices equipped with semiconductor devices. This kind of rise in temperature further increases the diffusion speed of the aforementioned substances, and will result in a significant problem where the functions of the electronic devices will deteriorate.
Moreover, generally speaking, the aforementioned titanium and its alloy film, titanium suicide film or titanium nitride film can be formed with a physical deposition method such as sputtering or vacuum deposition. Explained below is the sputtering method which is used most comprehensively among the above. This sputtering method is a method of physically colliding a positive ion such as Ar+ to a target disposed on a cathode and releasing the metal atoms constituting the target with the collision energy thereof.
Nitride may be formed by using titanium or its alloy (TiAl alloy, etc.) as the target and conducting sputtering under a mixed gas atmosphere of argon gas and nitrogen.
When impurities exist in the titanium (including alloys and compounds) target upon forming this sputtering film, coarsened particles floating in the sputtering chamber reach the substrate and cause disconnection or short circuit of the thin film circuit, increase the formation amount of particles that cause protrusions on the thin films, and, during sputtering in which gas components such as oxygen, hydrogen and nitrogen exist, cause abnormal electrical discharge thought to be caused by the outburst of such gases. Thus, there is a problem in that a uniform film cannot be formed.
Due to the forgoing problems, it goes without saying that it is necessary to reduce conventional impurities such as transition metal, high melting point metal, alkali metal, alkaline earth metal or other metals. Nevertheless, the aforementioned particles are formed even when decreasing the elements thereof as much as possible, and the current status is that the fundamental solution for such problems is yet to be discovered.
Furthermore, although there are cases where the titanium thin film is used as a pasting layer for preventing the formation of particles upon forming a titanium nitride Tixe2x80x94N film, the film is hard and sufficient adhesive strength could not be obtained, nor would it function as a pasting layer since it would peel off from the inner wall of the film-forming equipment or its components. Thus, there is a problem in that this would cause the formation of particles.
An object of the present invention is to overcome the various foregoing problems, and particularly to provide a titanium target for sputtering free from the formation of particles or occurrence of abnormal discharge phenomenon, having a reduced content of contaminants, and which is soft.
The present invention provides 1) a titanium target for sputtering wherein the oxygen contained in the titanium target for sputtering is 20 ppm or less and the average grain diameter of such target is 20 xcexcm or less; 2) a titanium target for sputtering wherein the impurity concentration of gas components such as oxygen, nitrogen and hydrogen contained in the titanium target is 20 ppm or less; 3) a titanium target for sputtering according to 1) or 2) above, wherein the Vickers hardness (Vs) is 120 or less; and 4) a titanium target for sputtering according to any one of 1) to 3) above, wherein the total content of alkali metal and alkaline earth metal such as Na and K is 5 ppm or less, the total content of heavy metal and light metal is 10 ppm or less, and the total content of radioactive elements such as U and Th of 1 ppb or less.